Translating core cowl having aerodynamic flap sections

ABSTRACT

An example core nacelle for a gas turbine engine includes a core cowl positioned adjacent an inner duct boundary of a fan bypass passage having an associated discharge airflow cross-sectional area. The core cowl includes at least one translating section and at least one flap section. The translating section of the core cowl is selectively moveable to vary the discharge airflow cross-sectional area.

BACKGROUND OF THE INVENTION

This invention generally relates to a gas turbine engine, and moreparticularly to a turbofan gas turbine engine having a translating corecowl for varying a discharge airflow cross-sectional area of the gasturbine engine.

In an aircraft gas turbine engine, such as a turbofan engine, air ispressurized in a compressor, and mixed with fuel and burned in acombustor for generating hot combustion gases. The hot combustion gasesflow downstream through turbine stages that extract energy from thegases. A high pressure turbine powers the compressor, while a lowpressure turbine powers a fan section disposed upstream of thecompressor.

Combustion gases are discharged from the turbofan engine through a coreexhaust nozzle, and fan air is discharged through an annular fan exhaustnozzle defined at least partially by a fan nacelle surrounding the coreengine. A significant amount of propulsion thrust is provided by thepressurized fan air which is discharged through the fan exhaust nozzle.The combustion gases are discharged through the core exhaust nozzle toprovide additional thrust.

A significant amount of the air pressurized by the fan section bypassesthe engine for generating propulsion thrust in turbofan engines. Highbypass turbofans typically require large diameter fans to achieveadequate turbofan engine efficiency. Therefore, the nacelle of theturbofan engine must be large enough to support the large diameter fanof the turbofan engine. Disadvantageously, the relatively large size ofthe nacelle results in increased weight, noise and drag that may offsetthe propulsive efficiency achieved by the high bypass turbofan engine.

It is known in the field of aircraft gas turbine engines that theperformance of the turbofan engine varies during diverse flightconditions experienced by the aircraft. Typical turbofan engines aredesigned to achieve maximum performance during normal cruise operationof the aircraft. Therefore, when combined with the necessity of arelatively large nacelle size, increased noise and decreased efficiencymay be experienced by the aircraft at non-cruise operating conditionssuch as take-off, landing, cruise maneuver and the like.

Accordingly, it is desirable to provide a turbofan engine having avariable discharge airflow cross-sectional area that achieves improvedengine performance and reduced flow disturbances of a fan dischargeairflow.

SUMMARY OF THE INVENTION

An example core nacelle for a gas turbine engine includes a core cowlpositioned adjacent an inner duct boundary of a fan bypass passagehaving an associated discharge airflow cross-sectional area. The corecowl includes at least one translating section and at least one flapsection. The translating section of the core cowl is selectivelymoveable to vary the discharge airflow cross-sectional area.

An example gas turbine engine system includes a fan nacelle having a fanexhaust nozzle, a core nacelle within the fan nacelle, a core cowlhaving a translating section and a flap section, a sensor that producesa signal representing an operability condition and a controller incommunication with the sensor to translate the core cowl between a firstposition and a second position. The first position includes a firstdischarge airflow cross-sectional area and the second position includesa second discharge airflow cross-sectional area greater than the firstdischarge airflow area. The core cowl is moved between the firstposition and the second position in response to detecting theoperability condition.

An example method of controlling a discharge airflow cross-sectionalarea of a gas turbine engine includes sensing an operability conditionand translating a core cowl in response to sensing the operabilitycondition. In one example, the operability condition includes at leastone of a takeoff condition and a landing condition.

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a general perspective view of an example gas turbineengine;

FIG. 2 is a schematic view of an example gas turbine engine having acore cowl moveable between a first position and a second position;

FIG. 3 illustrates an exploded cross-sectional view of an exampleconfiguration of the core cowl illustrated in FIG. 2; and

FIG. 4 illustrates a partial perspective view of an exampleconfiguration of the core cowl about an engine centerline axis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a gas turbine engine 10 suspends from an enginepylon 12 as is typical of an aircraft designed for subsonic operation.In one example, the gas turbine engine is a geared turbofan aircraftengine. The gas turbine engine 10 includes a fan section 14, a lowpressure compressor 15, a high pressure compressor 16, a combustor 18, ahigh pressure turbine 20 and a low pressure turbine 22. A low speedshaft 19 rotationally supports the low pressure compressor 15 and thelow pressure turbine 22 and drives the fan section 14 through a geartrain 23. A high speed shaft 21 rotationally supports the high pressurecompressor 16 and a high pressure turbine 20. The low speed shaft 19 andthe high speed shaft 21 rotate about a longitudinal centerline axis A ofthe gas turbine engine 10.

During operation, air is pressurized in the compressors 15, 16 and ismixed with fuel and burned in the combustor 18 for generating hotcombustion gases. The hot combustion gases flow through the high and lowpressure turbines 20, 22 which extract energy from the hot combustiongases.

The example gas turbine engine 10 is in the form of a high bypass ratio(i.e., low fan pressure ratio geared) turbofan engine mounted within afan nacelle 26, in which most of the air pressurized by the fan section14 bypasses the core engine itself for the generation of propulsionthrust. The example illustrated in FIG. 1 depicts a high bypass flowarrangement in which approximately 80% of the airflow entering the fannacelle 26 may bypass the core nacelle 28 via a fan bypass passage 27.The high bypass flow arrangement provides a significant amount of thrustfor powering the aircraft.

In one example, the bypass ratio is greater than ten, and the fansection 14 diameter is substantially larger than the diameter of the lowpressure compressor 15. The low pressure turbine 22 has a pressure ratiothat is greater than five, in one example. The gear train 23 can be anyknown gear system, such as a planetary gear system with orbiting planetgears, planetary system with non-orbiting planet gears, or other type ofgear system. In the disclosed example, the gear train 23 has a constantgear ratio. It should be understood, however, that the above parametersare only exemplary of a contemplated geared turbofan engine. That is,the invention is applicable to other engine architectures.

A fan discharge airflow F1 is communicated within the fan bypass passage27 and is discharged from the engine 10 through a fan exhaust nozzle 30,defined radially between a core nacelle 28 and the fan nacelle 26. Coreexhaust gases C are discharged form the core nacelle 28 through a coreexhaust nozzle 32 defined between the core nacelle 28 and a tail cone 34disposed coaxially therein around the longitudinal centerline axis A ofthe gas turbine engine 10.

The fan exhaust nozzle 30 concentrically surrounds the core nacelle 28near an aftmost segment 29 of the fan nacelle 26, in this example. Inother examples, the fan exhaust nozzle 30 is located farther upstreambut aft of the fan section 14. The fan exhaust nozzle 30 defines adischarge airflow cross-sectional area 36 between the fan nacelle 26 andthe core nacelle 28 for axially discharging the fan discharge airflow F1pressurized by the upstream fan section 14.

FIG. 2 illustrates a core cowl 38 of the gas turbine engine 10. The corecowl 38 represents an exterior flow surface of a section of the corenacelle 28. The core cowl 38 is positioned adjacent an inner ductboundary 25 of the fan bypass passage 27. The example core cowl 38includes a center section 40, and a plurality of leading edge flaps 42and trailing edge flaps 44 disposed circumferentially about enginecenterline axis A (See FIG. 4). In one example, the center section 40 ofthe core cowl 38 is positioned adjacent the fan exhaust nozzle 30 (e.g.,axially aligned). The actual positioning and configuration of the corecowl 38 will vary depending upon design specific parameters including,but not limited to, the size of the core nacelle and the efficiencyrequirements of the gas turbine engine 10.

In the illustrated example, the discharge airflow cross-sectional area36 extends between the aft most segment 29 of the fan nacelle 26adjacent to fan exhaust nozzle 30 and the center section 40 of the corecowl. Varying the discharge airflow cross-sectional area 36 of the gasturbine engine 10 during specific flight conditions provides improvedefficiency of the gas turbine engine 10 with minimal disturbance of thefan airflow F1 as the fan airflow F1 is communicated through the fanbypass passage 27, as is further discussed below. In one example, thedischarge airflow cross-sectional area 36 is varied by translating thecenter section 40 of the core cowl 38 forward (i.e., upstream) from itsposition adjacent the fan exhaust nozzle 30.

The core cowl 38 is moved from a first position X (i.e., the positionadjacent the fan exhaust nozzle 30, represented by phantom lines) to asecond position X′ (represented by solid lines) in response to detectingan operability condition of the gas turbine engine 10, in one example.In another example, the core cowl 38 is selectively moveable between aplurality of positions each having different discharge airflow crosssectional areas.

In the illustrated example, a discharge airflow cross-sectional area 46associated with the second position X′ is greater than the dischargeairflow cross-sectional area of the first position X. In one example,the operability condition includes a takeoff condition. In anotherexample, the operability condition includes a landing condition.However, the core cowl 38 may be translated between the first position Xand the second position X′, or any other position between the firstposition X and the second position X′, in response to any knownoperability condition.

A sensor 52 detects the operability condition and communicates with acontroller 54 to translate the core cowl 38 between the first position Xand the second position X′ via an actuator assembly 56. Of course, thisview is highly schematic. It should be understood that the sensor 52 andthe controller 54 are programmable to detect known flight conditions. Aperson of ordinary skill in the art having the benefit of the teachingsherein would be able to program the controller 54 to communicate withthe actuator assembly 56 to translate the core cowl 38 between the firstposition X and the second position X′.

The distance the core cowl 38 translates in response to detecting theoperability condition will vary depending on design specific parameters.The actuator assembly 56 returns the center section 40 of the core cowl38 to the first position X during normal cruise operation (e.g., agenerally constant speed at generally constant, elevated altitude) ofthe aircraft. The discharge airflow cross-sectional area 46 permits anincreased amount of fan airflow F1 to exit the fan exhaust nozzle 30 ascompared to the discharge airflow cross-sectional area 36. Therefore,the design of the fan section 14 may be optimized for diverseoperability conditions of the aircraft.

FIG. 3 illustrates an example configuration of the core cowl 38. Theexample center section 40 of the core cowl 38 is slidably secured to astationary section 50 of the core cowl 38. The center section 40 isaxially translatable along the stationary section 50 of the core cowl 38in a direction parallel to the longitudinal centerline axis A.

The stationary section 50 includes a cavity 60 for storing the actuatorassembly 56. In one example, the actuator assembly 56 includes internallinkages. In another example, the actuator assembly 56 includes a ballscrew. The actuator assembly 56 may use hydraulic, electromechanical,electrical or any other power source to translate the center section 40of the core cowl 38.

A leading edge 62 of the leading edge flap 42 is affixed to thestationary section 50 of the core cowl 38. In one example, the leadingedge 62 of the leading edge flap 42 is affixed to the stationary section50 of the core cowl via a hinged mount. The trailing edge 64 of theleading edge flap 42 is not affixed to the core cowl 38. That is, thetrailing edge 64 of the leading edge flap 42 is movable along anexterior surface 66 of the center section 40 as the center section 40 istranslated between positions X and X′.

A leading edge 68 of the trailing edge flap 44 is affixed to the centersection 40 of the core cowl 38. In one example, the leading edge 68 isaffixed to the center section 40 via a hinged mount. The trailing edge70 of the trailing edge flap 44 is not affixed to the core cowl 38. Thatis, the trailing edge 70 of the trailing edge flap 44 is free totranslate along an exterior surface 72 of the stationary section 50 asthe center section 40 translates between positions X and X′. It shouldbe understood that an opposite configuration, in which the trailingedges 64, 70 of the edge flaps 42, 44 are affixed to the core cowl 38and the leading edges 62, 68 are free to translate with respect to thecore cowl 38, is contemplated as within the scope of this invention.

Although slideable along portions of the core cowl 38, the leading edges62, 68 of the leading edge flap 42 and the trailing edge flap 44 areprevented from lifting away from the core cowl 38 and creating a gapbetween the edge flaps 42, 44 and the core cowl 38 by the downstreamflowing fan airflow F1. In one example, the core cowl 38 includes aplurality of the edge flaps 42, 44 that are circumferentially spacedabout the longitudinal centerline axis A of the gas turbine engine (SeeFIG. 4). The edge flaps 42, 44, due in part to their circumferentialspacing and in part to their slideable trailing edges 64, 70, maintainan aerodynamic flow surface for the fan airflow F1 as the fan airflow F1is communicated downstream within the fan bypass passage 27.Advantageously, flow disturbance of the fan airflow F1 is minimizedresulting in improved engine operability and efficiency.

The edge flaps 42, 44 optionally comprise a shape memory alloy having afirst solid phase that corresponds to a first shape of the edge flaps42, 44 and a second solid state that corresponds to a second shape ofthe edge flaps 42, 44. For example, the shape memory alloy is thermallyor magnetically active to reversibly transition the shape memory alloybetween the phases to change the shape of the edge flaps 42, 44.

In one example, the entire surfaces of the edge flaps 42, 44 include ashape memory alloy. In another example, only the leading edges 62, 68and the trailing edges 64, 70 of the edge flaps 42, 44 include a shapememory alloy.

One example thermally active shape memory alloy includes anickel-titanium alloy. A second example thermally active shape memoryalloy includes a copper-zinc-aluminum alloy. Yet another examplethermally active shape memory alloy includes a copper-aluminum-nickelalloy. One example magnetically active shape memory alloy includes anickel-manganese-gallium alloy. However, other shape memory alloys maybe utilized, as would be understood by those of skill in the art havingthe benefit of this disclosure. In combination with a source thatprovides heat or a magnetic field, the shape memory alloy furtherenhances the flow contours of the core cowl 38 for improved flow of thefan airflow F1 through the fan bypass passage 27 and provides improvedsealing between the center section 40 and the edge flaps 42, 44.

The foregoing description shall be interpreted as illustrative and notin any limiting sense. A worker of ordinary skill in the art wouldrecognize that certain modifications would come within the scope of thisinvention. For that reason, the follow claims should be studied todetermine the true scope and content of this invention.

What is claimed is:
 1. A core nacelle comprising: a core cowl positionedadjacent an inner duct boundary of a fan bypass passage having anassociated discharge airflow cross-sectional area, wherein said corecowl includes a center section and at least one flap section in contactwith an exterior surface of said center section, said center sectionbeing selectively axially translatable to vary said discharge airflowcross-sectional area.
 2. The core nacelle as recited in claim 1, whereinsaid discharge airflow cross-sectional area is defined between an innersurface of a fan nacelle and an outer surface of said center section. 3.The core nacelle as recited in claim 1, wherein said at least one flapsection includes a first flap and a second flap aft of said first flap,wherein a leading edge of one of said first flap and said second flap isaffixed to said core cowl and a leading edge of the other of said firstflap and said second flap is affixed to said center section of said corecowl.
 4. The core nacelle as recited in claim 3, wherein a trailing edgeof each of said first flap and said second flap is slideable relative toone of said center section and said core cowl to provide an aerodynamicflow surface for a fan airflow.
 5. The core nacelle as recited in claim4, wherein at least said leading edges and said trailing edges of saidfirst flap and said second flap comprise a shape memory alloy having afirst solid state phase that corresponds to a first shape of said firstflap and said second flap and a second solid state phase thatcorresponds to a second shape of said first flap and said second flap.6. The core nacelle as recited in claim 3, wherein said center sectionof said core cowl is moveable to vary said discharge airflowcross-sectional area, wherein one of said first flap and said secondflap slides against said center section and the other of said first flapand said second flap slides against a stationary section of said corecowl in response to moving said at center section.
 7. The core nacelleas recited in claim 1, wherein said at least one flap section includes aplurality of flap sections, wherein said plurality of flap sections arecircumferentially spaced about a longitudinal centerline axis of a gasturbine engine.
 8. A gas turbine engine system, comprising: a fannacelle defined about an axis and having a fan exhaust nozzle; a corenacelle having a core cowl including a center section and at least oneflap section, wherein said center section of said core cowl isselectively axially moveable between a first position having a firstdischarge airflow cross-sectional area and a second position having asecond discharge airflow cross-sectional area greater than said firstdischarge airflow cross-sectional area; a turbofan positioned withinsaid fan nacelle; a gear train that drives at least said turbofan; atleast one compressor and at least one turbine positioned downstream ofsaid turbofan; at least one combustor positioned between said at leastone compressor and said at least one turbine; at least one sensor thatproduces a signal representing an operability condition; and acontroller that receives said signal, wherein said controllerselectively moves said center section of said core cowl between saidfirst position and said second position in response to said signal. 9.The system as recited in claim 8, comprising an actuator assembly incommunication with said controller and operable to move said centersection of said core cowl between said first position and said secondposition.
 10. The system as recited in claim 9, wherein said actuatorassembly is mounted within a cavity of a stationary section of said corecowl, wherein said actuator assembly includes at least one of a ballscrew and internal linkages.
 11. The system as recited in claim 8,wherein said second position is upstream from said first position. 12.The system as recited in claim 8, wherein said center section is axiallytranslatable between said first position and said second position. 13.The system as recited in claim 8, wherein said center section is axiallymoveable between a plurality of positions between said first positionand said second position.
 14. The system as recited in claim 8, whereinsaid operability condition includes at least one of a take-off conditionand a landing condition.
 15. A method of controlling the dischargeairflow cross-sectional area of a gas turbine engine, comprising thesteps of: (a) sensing an operability condition; and (b) selectivelyaxially translating a center section of a core cowl to vary thedischarge airflow cross-sectional area of a fan bypass passage inresponse to sensing the operability condition.
 16. The method as recitedin claim 15, wherein the operability condition includes at least one ofa take-off condition and a landing condition.
 17. The method as recitedin claim 15, wherein the center section is selectively moveable betweena first position having a first discharge airflow cross-sectional areaand a second position having a second discharge airflow cross-sectionalarea greater than the first discharge airflow area, wherein said step(b) comprises: translating the center section of the core cowl assemblyfrom the first position to the second position in response to sensingthe operability condition.
 18. The method as recited in claim 17,comprising the step of: (c) returning the center section of the corecowl to the first position in response to detection of a cruiseoperation.
 19. The method as recited in claim 15, wherein the core cowlincludes a stationary section, the center section, at least one leadingedge flap and at least one trailing edge flap and said step (b)comprises: moving the center section of the core cowl in an upstreamdirection; sliding one of the at least one leading edge flap and the atleast one trailing edge flap along an exterior surface of the centersection; and sliding the other of the at least one leading edge flap andthe at least one trailing edge flap along the stationary section of thecore cowl.
 20. The core nacelle as recited in claim 1, wherein saidcenter section is slidably secured to a stationary section of said corecowl, and said center section is axially translatable along saidstationary section of said core cowl in a direction parallel to alongitudinal centerline axis of said core cowl.